• Chromic oxide contamination of pasture previously used in marker studies

      Sprinkle, J. E.; Kress, D. D.; Doornbos, D. E.; Anderson, D. C.; Tess, M. W.; Ansotegui, R. P.; Olson, B. E.; Roth, N. J. (Society for Range Management, 1995-05-01)
      Fecal output of range cows was determined during 2 periods of summer (period I) and late summer (period II) grazing using a constant release intraruminal Cr2O3 bolus. Chromic oxide contamination was determined by analyzing forage for Cr2O3 and by obtaining fecal samples from cows prior to bolusing. Control cows were also monitored along with the experimental cows during grazing periods. The overall herd least squares mean for fecal output during period I was lower than the expected value by 48%. Forage during period I contained an average of 55.7 microgram Cr2O3 g-1 of forage or about 45% of the daily dose of the bolus. Forage during period II contained an average of 38.3 microgram Cr2O3 g-1 of forage or about 29% of the daily dose of the bolus. Our results indicate that comparisons of fecal output least squares means by period of the year can be biased by Cr2O3 contamination of forage in pastures which have been previously used for marker studies.
    • Herbage dynamics on 2 Northern Great Plains range sites

      Heitschmidt, R. K.; Grings, E. E.; Haferkamp, M. R.; Karl, M. G. (Society for Range Management, 1995-05-01)
      Quantity and quality of forage produced are primary determinants of level of livestock production derived from grazing lands. Moreover, species composition of herbage is often considered a primary determinant of the ecological condition of rangelands. The broad objective of this study was to quantify the productivity, growth dynamics, and quality of herbage growing on 2 Northern Great Plains range sites and to concurrently relate magnitude and composition of production to the ecological condition of the sites. Using frequent harvest techniques, the 2-year study showed herbage production on the highly productive silty range site averaged 219 g m-2 as compared to 218 g m-2 on the supposedly less productive clay pan range site. The primary reason the clay pan site proved to be as productive as the silty site was attributed to the greater amounts of introduced annual grasses on the clay pan (148 g m-2) than the silty site (104 g m-2). The annual grass component on the clay pan was a near equal mix (71 vs 51 g m-2) of Japanese brome (Bromus japonicus Thunb.) and cheatgrass (B. tectorum L.) whereas the overwhelming dominant on the silty site was cheatgrass (73 g m-2). Western wheatgrass [Pascopyrum smithii Rydh. (Love)] was the dominant perennial grass on both sites averaging 49 g m-2 on the clay pan site and 57 g m-2 on the silty site. There were minimal differences between sites in terms of nutrient quality values (i.e., crude protein, acid detergent fiber, neutral detergent fiber) with results showing clearly that age of tissue was the major factor altering seasonal forage quality values. Range condition analyses revealed the clay pan site was in fair ecological condition and the silty site was in good condition. Study results demonstrate the need for land management agencies to continue to refine productivity estimates as well as adopt new techniques for assessing the ecological condition of rangelands.